Magnetoresistance effect element and method for producing same

ABSTRACT

There is provided a magnetoresistance effect element which is capable of causing a large sense current to flow between electrodes and which has a smaller dispersion in direction of magnetization of a CPP element based on a magnetic field due to the sense current and has a lager reproducing output, and a method for producing the same. The magnetoresistance effect element is produced by: after forming a first electrode, forming a magnetoresistance effect film on the first electrode; applying a self-condensing organic resist on the magnetoresistance effect film, and thereafter, causing the organic resist to be droplets; subsequently, forming an insulating film thereon, and thereafter, removing the organic resist to form a groove portion in the insulating film to expose the top surface of the magnetoresistance effect film; and filling the groove portion with an electrode material to form a second electrode.

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Applications No. 2001-26028, filed on Feb. 1,2001; the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a magnetoresistance effectelement and a method for producing the same.

2. Description of Related Art

In recent years, the density of information recorded in a magneticrecording medium has been increased. In HDD (Hard Disk Drive) units, asystem having a high packing density of 10 Gbpsi (Gigabit per squareinch) has been put to practical use, and a system having a higherpacking density has been required. As a countermeasure thereto, it isimportant to form a narrow track having a width of 1 μm in a magnetichead. Also in a recording and/or reproducing thin-film magnetic head,various proposals for structure have been made in order to achieve anarrow track. However, it is said that a magnetic packing densitycapable of being applied to the structure of a conventionally proposedrecording and/or reproducing thin-film magnetic head is limited to about100 to 200 Gbpsi. In order to further increase the magnetic packingdensity, it is required to provide a magnetic gap having a size of 0.1μm or less and a high reproducing output. However, it is very difficultto realize such a magnetic gap and a high reproducing output in aconventionally proposed recording and/or reproducing thin-film magnetichead.

Therefore, in order to solve these problems, a horizontal thin-filmmagnetic head and a CPP (Current Perpendicular to the Plane) typemagnetoresistance effect film material having a large magnetoresistanceeffect have been proposed in Japanese Patent Laid-Open Nos. 11-120509and 11-25433 and Outline of 24-th Lecture of Japan Applied MagnetismInstitution (2000), page 427.

FIG. 5 is a schematic diagram most simply showing a CPP typemagnetoresistance effect element (which will be also hereinafterreferred to as a CPP element). That is, this CPP element 40 has astructure wherein a bottom electrode 41 and a top electrode 45 areformed on the top and bottom of a CPP type magnetoresistance effect film43, an insulator (not shown) being formed around the bottom and topelectrodes 41 and 45. Because of such a structure, a reproducing currentI caused to flow through the bottom electrode 41 is separated into acurrent I1 flowing through the CPP type magnetoresistance effect film 43and a leakage current I2 flowing between the top and bottom electrodes41 and 45 to flow into the top electrode 45. At this time, with respectto the output of the CPP type magnetoresistance effect film 43, only avariation in resistance due to the current I1 is detected as a variationin voltage.

In the thin-film magnetic head using the CPP element 40 wherein acurrent is applied in a direction perpendicular to the plane of thefilm, the thickness of the insulator decreases as the thickness of thereproducing element (CPP element) decreases. In accordance therewith,the distance between the electrodes 41 and 45 for sandwiching thereproducing element therebetween decreases, and the possibility ofincreasing a leakage current flowing through the insulator other than acurrent flowing through the reproducing element increases. Therefore, inorder to solve such a problem, it is required to develop a CPP typemagnetoresistance effect film material capable of obtaining a highreproducing output with a small current and an insulating materialhaving a high withstand voltage. However, it is not easy to achieve thepurposes therefor.

FIG. 6 shows the cross-sectional structure of an actual reproducingmagnetic head when the CPP element 40 is applied to the head. In theconstruction of the reproducing magnetic head, magnetization informationis sucked up from a medium (not shown) by a reproducing magnetic yoke 48to be propagated to the CPP element 40, and the resistance changes bythe change in direction of magnetization at that time. In FIG. 6, amagnetization fixing layer 47 is formed on the side portion of the CPPtype magnetoresistance effect film 43. Also in this case, in FIG. 6,when a reproducing current is caused to flow, the direction ofmagnetization of the CPP element 40 fluctuates by a magnetic field dueto current from a corner portion of the top electrode 45, so that it isnot possible to obtain a high reproducing output.

On the other hand, as a magnetoresistance effect element using the sameprinciple as that of the CPP element, there is a TMR (TunnelingMagneto-Resistance) element. In the case of the TMR element, aninsulator of Al₂O₃ or the like is used as a junction. Since thisinsulator has a very small thickness of about 1 nm, it is not requiredto cause a sense current, which flows through the TMR element, to belarger than that of the CPP element, and it is not required to increasethe withstand voltage of a surrounding insulator in the TMR element.

On the other hand, it is required to cause a large sense current to flowthrough the CPP element 40 in order to obtain a high reproducing output.In this case, the magnetic field due to sense current is very large todisturb the direction of magnetization of the magnetization fixing layer47 and to form the CPP type magnetoresistance effect film 43. Since thedirection of magnetization of a magneto-sensitive layer havingmagnetization disperses, there is a problem in that the detectionsensitivity greatly decreases. As an example, the relationship betweenthe sense currents of a TMC element and CPP element and the magneticfields due to the currents is shown in FIG. 7. As shown in FIG. 7, inorder to obtain a necessary and sufficient reproducing output, the sensecurrent of the CPP element must be about ten times as large as that ofthe TMR element. In accordance therewith, the magnetic field due tocurrent, which is applied to the CPP element and which is produced inthe vicinity of the CPP element is a very large magnetic field of 50 to1000 times as large as that of the TMR element.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to eliminate theaforementioned problems and to provide a magnetoresistance effectelement which is capable of causing a large sense current to flowbetween electrodes and which has a smaller dispersion in direction ofmagnetization of a CPP element based on a magnetic field due to thesense current and has a lager reproducing output, and a method forproducing the same.

In order to accomplish the aforementioned and other objects, accordingto a first aspect of the present invention, there is provided a methodfor producing a magnetoresistance effect element comprising: afterforming a first electrode, forming a magnetoresistance effect film onthe first electrode; applying a self-condensing organic resist on themagnetoresistance effect film, and thereafter, causing the organicresist to be droplets; subsequently, forming an insulating film thereon,and thereafter, removing the organic resist to form a groove portion inthe insulating film to expose the top surface of the magnetoresistanceeffect film; and filling the groove portion with an electrode materialto form a second electrode.

According to such a method for producing magnetoresistance effectaccording to the first aspect of the present invention, the grooveportion formed in the insulating film leaves the magnetoresistanceeffect film as approaching the periphery of the magnetoresistance effectfilm, so that the distance between the first and second electrodesincreases as approaching the periphery of the magnetoresistance effectfilm. Thus, even if a large current is caused to flow between the firstand second electrodes, it is possible to prevent the direction ofmagnetization of a magnetization fixing film, which is formed on theside portion of the magnetoresistance effect film, from being disturbedby a magnetic field due to the current, and it is possible to decreasethe dispersion in direction of magnetization of the magnetoresistanceeffect film. In addition, it is possible to decrease a leakage currentfrom the corner portions of the first and second electrodes, so that itis possible to cause a large sense current to flow between theelectrodes and obtain a high reproducing output.

Furthermore, for example, the magnetoresistance effect films accordingto the present invention include giant magnetoresistance effect filmsand tunneling magnetoresistance effect films which have a ferromagneticlayer, a non-magnetic layer and a ferromagnetic layer and wherein theelectric resistance of the whole magnetoresistance effect film varies inaccordance with the variation in relative direction of magnetization ofthe ferromagnetic layers facing each other via the non-magnetic layer.If the non-magnetic layer is a conductive non-magnetic layer of Cu orthe like, the magnetoresistance effect film can be widely used as acurrent perpendicular to the plane type giant magnetoresistance film fora magnetic storage, a magnetoresistance effect head, a magnetic sensoror the like. If the non-magnetic layer contains a dielectric, such asalumina or an oxide film, a tunneling current flows between bothferromagnetic layers via the dielectric, so that the magnetoresistanceeffect can be widely used as a tunneling magnetoresistance effect filmfor a magnetic storage, a magnetic head, a magnetic sensor or the like.

According to a second aspect of the present invention, there is provideda method for producing a magnetoresistance effect element comprising:after forming a first electrode, forming a magnetoresistance effect filmon the first electrode; forming an insulating film on themagnetoresistance effect film; and using a mask having an openingportion, the position of which matches with the position of themagnetoresistance effect film, to isotropic-etch the insulating film toform a curved recessed portion in the insulating film to expose the topsurface of the magnetoresistance effect film to form a second electrodein the recessed portion.

According to such a method for producing magnetoresistance effectaccording to the first aspect of the present invention, the mask havingthe opening portion, the position of which matches with the position ofthe magnetoresistance effect film, is used for isotropic-etching theinsulating film formed on the magnetoresistance effect film, so that thecurved recessed portion is formed in the insulating film to form thesecond electrode in the recessed portion. Therefore, the positioningaccuracy of the magnetoresistance effect film to the second electrode isimproved, and the second electrode having a good shape converging towardthe magnetoresistance effect film is obtained, so that the distancebetween the first and second electrodes increases as approaching theperiphery of the magnetoresistance effect film. Thus, even if a largecurrent is caused to flow between the first and second electrodes, it ispossible to prevent the direction of magnetization of a magnetizationfixing film, which is formed on the side portion of themagnetoresistance effect film, from being disturbed by a magnetic fielddue to the current, and it is possible to decrease the dispersion indirection of magnetization of the magnetoresistance effect film. Inaddition, it is possible to decrease a leakage current from the cornerportions of the first and second electrodes, so that it is possible tocause a large sense current to flow between the electrodes and obtain ahigh reproducing output.

Furthermore, the second electrode is preferably formed by forming aconverging opening portion, which is communicated with themagnetoresistance effect film, in the insulating film by an anisotropicetching after forming a curved recessed portion, and by filling theopening portion and the recessed portion with an electrode materialfilm.

Thus, since the converging opening portion communicated with themagnetoresistance effect film is formed in the insulating film by theanisotropic etching, the second electrode further converges toward themagnetoresistance effect film, so that it is possible to cause a largersense current to flow between the electrodes and obtain a largerreproducing output.

According to a third aspect of the present invention, there is provideda magnetoresistance effect element comprising: a first electrode whichhas a first protruding portion having a substantially flat top face; acurrent perpendicular to the plane type magnetoresistance effect film,one end of which is electrically connected to the top face of said firstelectrode; and a second electrode which has a second protruding portionhaving a substantially flat top face, the second protruding portionbeing electrically connected to the other end of the magnetoresistanceeffect film, wherein the first and second protruding portions haveshapes converging toward the magnetoresistance effect film in a crosssection perpendicular to the film plane of the magnetoresistance effectfilm.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given herebelow and from the accompanying drawings of theembodiments of the invention. However, the drawings are not intended toimply limitation of the invention to a specific embodiment, but are forexplanation and understanding only.

In the drawings:

FIGS. 1(a) through 1(c) are sectional views showing producing steps inthe first embodiment of a method for producing a magnetoresistanceeffect element according to the present invention;

FIGS. 2(a) through 2(d) are sectional views showing producing steps inthe first embodiment of a method for producing a magnetoresistanceeffect element according to the present invention;

FIGS. 3(a) through 3(d) are sectional views showing producing steps inthe second embodiment of a method for producing a magnetoresistanceeffect element according to the present invention;

FIG. 4 is a graph showing a reproducing output to a making current in athin-film magnetic head, which uses a magnetoresistance effect elementproduced by a embodiment of a producing method according to the presentinvention, and in a conventional thin-film magnetic head;

FIG. 5 is a sectional view showing the construction of a CPP typemagnetoresistance effect element;

FIG. 6 is a sectional view showing the construction of a currentperpendicular to the plane type thin-film magnetic head;

FIG. 7 is a table showing the relationship between the sense currents ofa TMR element and CPP element and the magnetic field due to thecurrents;

FIG. 8 is a sectional view showing the construction of the thirdembodiment of a magnetoresistance effect element according to thepresent invention;

FIGS. 9(a) through 9(d) are sectional views showing steps of producingthe third embodiment of a magnetoresistance effect element according tothe present invention;

FIGS. 10(a) through 10(d) are sectional views showing steps of producingthe third embodiment of a magnetoresistance effect element according tothe present invention; and

FIGS. 11(a) through 11(d) are sectional views showing steps of producingthe third embodiment of a magnetoresistance effect element according tothe present invention.

DESCRIPTION OF THE EMBODIMENTS

Referring now to the accompanying drawings, the embodiments of a methodfor producing a magnetoresistance effect element according to thepresent invention will be described below.

(First Embodiment)

Referring to FIGS. 1 and 2, the first embodiment of a method forproducing a magnetoresistance effect element according to the presentinvention will be described below. FIGS. 1 and 2 are sectional viewsshowing producing steps in the first embodiment.

First, as shown in FIG. 1(a), an insulating film 4 having a thickness of50 nm to 500 nm is formed on a substrate 2. In this case, the insulatingfilm 4 may be formed of an oxide, such as SiO₂ or Al₂O₃, a nitride, suchas Si₃N₄ or AlN, or an oxide nitride which is a mixture thereof, and maybe formed by a usual sputtering method or CVD (Chemical VaporDeposition) method. In this embodiment, the insulating film 4 of SiO₂having a thickness of 100 nm was formed by the RF (Radio Frequency)magnetron sputtering method, by using a target of Si, by the reactivesputtering and by feeding oxygen. Subsequently, in order to form agroove for a reproducing yoke, a resist pattern (not shown) having anaperture width of 50 nm to 500 nm is prepared by a usual lithographytechnique, and a tapered groove is prepared in the insulating film 4.Then, the resist is removed (see FIG. 1(a)). In this embodiment, after aresist pattern (not shown) having an aperture width of 400 nm was formedby an I-line stepper, etching was carried out by the RIE (Reactive IonEtching) using CHF₃ as an etching gas at a making power of 150 W at apressure of 2 Pa, a reproducing yoke forming groove having a taperedangle of about 80 degrees was formed in the insulating film 4. In thiscase, the etching method may be any one of the ICP (Inductivity CoupledPlasma) method, the IBE (Ion Beam Etching) method and the RIBE (ReactiveIon Beam Etching) method in addition to the RIE method used in thisembodiment, and should not particularly be limited.

Then, as shown in FIG. 1(a), when a reproducing magnetic yoke materialfilm 6 is formed on the whole surface of the substrate, the reproducingmagnetic yoke material film 6 on the groove is recessed to form arecessed portion 7. In this case, the material of the reproducingmagnetic yoke should not particularly be limited. The material of thereproducing magnetic yoke may be a material which is a magnetically softmaterial having a relatively large magnetic permeability and a smallanisotropy, e.g., a microcrystal ferroalloy which has magnetically softcharacteristics and which is selected from an Ni—Fe alloy, such asNi₈₀Fe₂₀ [at %] (commonly called Permalloy), an FeAlSi (commonly calledSendust) or FeZr(Ta)N alloy, and an Fe—Cu—M—Si—B alloy (commonly calledFinemet, and M is any one of Ta, Nb, Mo, W, Zr and Hf). As a layerunderlying the reproducing magnetic yoke, an diamagnetic material (e.g.,PtMn, PdMn, PtPdMn) or the like may be formed in order to form a singlemagnetic domain and stabilize the magnetic anisotropy. In addition, theforming method should not particularly be limited. The forming methodmay be any one of usual methods, such as the RF magnetron sputteringmethod, the ion beam sputtering method, the MBE (Molecular Beam Epitaxy)method and the CVD method, if it can form a film having a small numberof defects in the reproducing magnetic yoke forming groove. Morepreferably, in order to improve the magnetic characteristics of thereproducing magnetic yoke, the film may be deposited by applying amagnetic field and raising the temperature of the substrate. In thisembodiment, the reproducing magnetic yoke material film 6 of Permalloyhaving a thickness of 100 nm was deposited by the IBS (Ion Beam Sputter)method with Ar ion beams under a pressure of 1×10⁻⁴ Torr while applyinga magnetic field into the plane of the film. After a buried state of thereproducing magnetic yoke material film 6 of Permalloy formed in thegroove was verified on its cross section by a transmission electronmicroscope, it was verified that the reproducing magnetic yoke materialfilm 6 had little defect. In addition, after the magneticcharacteristics of the reproducing magnetic yoke material film 6 weremeasured by a B-H loop tracer, it was verified that the reproducingmagnetic yoke material film 6 has good magnetically soft characteristicsthat the coercive force was 1 Oe or less and the anisotropic magneticfield was 5 Oe.

Then, as shown in FIG. 1(b), a lithography technique, e.g., the IBE (IonBeam Etching) method, is used for patterning the reproducing magneticyoke material film 6 to form a reproducing magnetic yoke 6 a.Thereafter, a reproducing magnetic gap 8 is formed in the reproducingmagnetic yoke 6 a by the FIB (Focused Ion Beam) method or the like.Furthermore, in FIG. 1(b) and the subsequent figures, the substrate 2 isomitted. Alternatively, the reproducing magnetic gap 8 may be formedafter depositing the reproducing magnetic yoke material film 6, andthereafter, the reproducing magnetic yoke material film 6 may bepatterned to prepare the reproducing magnetic yoke 6 a. The reproducingmagnetic gap 8 may be prepared by another method, such as the RIE methodor the RIBE method. In this embodiment, the reproducing magnetic gap 8was formed by the FIB method so as to have a width of 50 nm. Then, abottom electrode forming resist pattern (not shown) is formed so that aregion including the recessed portion 7 on the reproducing magnetic yoke6 a is an opening portion. Subsequently, a film of, e.g., Cu, isdeposited on the whole surface so as to have a thickness of about 100nm, and thereafter, the resist pattern is removed to form a bottomelectrode forming film 10 of Cu (see FIG. 1(b)). Thereafter, aninsulating film 12 is formed on the whole surface. In this embodiment,an Al2O3 film having a thickness of 200 nm was used as the insulatingfilm 12. As the insulating material, an oxide, such as SiO₂ or (Si,Al)O_(x), may be used. Then, the insulating film 12 and the bottomelectrode forming film 10 are polished and flattened by, e.g., the CMP(Chemical Mechanical Polishing), until the film surface of thereproducing magnetic yoke 6 a is exposed, so that a bottom electrode 10a buried in the recessed portion 7 of the reproducing magnetic yoke 6 ais formed as shown in FIG. 1(c). After the surface flattened by the CMPwas measured by an AFM (Atomic Force Microscope), it was verified thatthe surface had a surface roughness of 10 nm or less and good surfaceperformance.

Then, as shown in FIG. 2(a), after a CPP type magnetoresistance effectmaterial film is formed on the whole surface of the substrate, a CPPtype magnetoresistance effect film forming resist pattern 16 is formedby lithography in a region which covers the bottom region 10 a on theCPP type magnetoresistance effect material film. The resist pattern 16used in this embodiment has a width of 0.8 μm and a resist thickness of0.9 μm. The resist pattern 16 is used as a mask for etching the CPP typemagnetoresistance effect material film until the reproducing magneticyoke 6 a is exposed, so that a CPP magnetoresistance effect film 14 isformed in a region which covers the bottom electrode 10 a. Subsequently,the remaining resist pattern 16 is etched by, e.g., the isotropicetching, so that the resist pattern 16 on the CPP magnetoresistanceeffect film 14 has a width of 0.6 μm and a resist thickness of 0.7 μm(see FIG. 2(a)). Thereafter, a magnetization fixing film forming resistpattern 17 is formed on the insulating film 12.

Then, after a magnetization fixing material film of CoPt alloy having athickness of 50 nm is formed on the whole surface by a usual spatteringmethod, the CPP type magnetoresistance effect forming resist pattern 16and the magnetization fixing film forming resist pattern 17 are removedto obtain a magnetization fixing film 18 which overlaps with a part ofthe top face of the CPP type magnetoresistance effect film 14 as shownin FIG. 2(b).

Then, a surface treatment is carried out so that the exposed surface ofthe CPP type magnetoresistance effect film 14 is hydrophilic. As thistreatment method, a plasma treatment or a chemical treatment is used.This hydrophilic treatment is carried out so that the surface of themagnetization fixing film 18 is water repellent (hydrophobic). Then,after an self-condensing organic resist 20 is applied on the wholesurface of the substrate as shown in FIG. 2(c), temperature is raisedfrom 100° C. to 200° C. to cause the self-condensing organic resist 20to self-condense on the CPP type magnetoresistance effect film 14 to bedroplets. Furthermore, the self-condensing organic resists include apolystyrene-polymethylmethacrylate and a polybutadiene-polystyrene.Subsequently, after an insulating film 22 of, e.g., Al₂O₃, having athickness of 1 μm is formed on the whole surface by, e.g., thesputtering method or the CVD method, the droplet-like organic resist 20is removed, so that a groove for forming a curved electrode is formed inthe insulating film 22. Then, an electrode film of, e.g., Cu, is formedin the groove to carry out a flattening treatment to form a topelectrode 24, which has a shape converging toward the CPP typemagnetoresistance effect film 14, on the CPP type magnetoresistanceeffect film 14 as shown in FIG. 2(d). Thereafter, the substrate 2 (notshown) is peeled off to obtain a current perpendicular to the plane typethin-film magnetic head. Furthermore, the method for forming theinsulating film 22 may be a depositing method by which the droplet-likeorganic resist 20 is not deformed by heat or the like.

As described above, according to the producing method in thisembodiment, the electrode 24 formed on the CPP type magnetoresistanceeffect film 14 has a shape converging toward the CPP typemagnetoresistance effect film 14, so that the distance between the topand bottom electrodes 10 a and 24 increasing as approaching themagnetization fixing film 18. Thus, even if a large current is caused toflow between the bottom electrode 10 a and the top electrode 24, it ispossible to prevent the direction of magnetization of the magnetizationfixing film from being disturbed by the magnetic field due to thecurrent, and it is possible to decrease the dispersion in direction ofmagnetization of the CPP type magnetoresistance effect film 14. Inaddition, it is possible to decrease the leakage current from the cornerportions of the electrodes 10 a and 24 to cause a large sense current toflow between the electrodes 10 a and 24, and it is possible to obtain ahigh reproducing output.

(Second Embodiment)

Referring to FIG. 3, the second embodiment of a method for producing amagnetoresistance effect element according to the present invention willbe described below. FIGS. 3(a) through 3(d) are sectional views showingproducing steps in the second embodiment.

In the producing method in this second embodiment, a magnetizationforming film 18 is formed so as to overlap with a part of a CPP typemagnetoresistance effect film 14 by the same method as that in the firstembodiment.

Subsequently, in FIG. 3(a), an insulating film 30 is formed on the wholesurface of the substrate. In this case, the insulating film 30 of SiO₂having a thickness of 2 μm was formed by the reactive sputtering method.The material of the insulating film 30 may be another material, andshould not particularly be limited. Thereafter, as shown in FIG. 3(a), aresist pattern 32 which has an opening portion having a width of about0.3 μm in a region on the insulating film 30 corresponding to theposition of a reproducing magnetic gap 8 and which has a thickness of0.3 μm is formed. That is, the resist pattern 32 has an opening portion,the position of which matches with that of the CPP typemagnetoresistance effect film 14.

Then, as shown in FIG. 3(b), the resist pattern 32 is used as a mask foretching the insulating film 30 by an isotropic etching, such as the CDE(Chemical Dry Etching), to form a curved recessed portion 34 in theinsulating film 30. Subsequently, as shown in FIG. 3(c), the resistpattern 30 is used as a mask for further etching the insulating film 30by the anisotropic etching until the surface of the CPP typemagnetoresistance effect film 14 is exposed, so that an opening portion35 communicated with the CPP type magnetoresistance effect film 14 isformed in the insulating film 30. In this embodiment, the isotropicetching was carried out by a depth of about 1 μm at a pressure of 70 Pausing CF₄ gas and CDE. By this etching, the resist thickness of theresist pattern 32 was decreased by about 0.05 μm (see FIG. 3(b)). Then,the resist pattern 32 having a resist thickness of 0.25 μm was used as amask for anisotropic-etching the insulating film 30 of SiO₂ in a depthdirection by about 0.4 μm by the RIE method at a pressure of 1 Pa usinga gas kind of CHF₃. Thus, as shown in FIG. 3(c), electrode formingcontact holes 34 and 35 having a curved shape and a converging shape areformed in the insulating film 30.

Then, after the resist pattern 32 is removed, an electrode material,e.g., Cu, is buried in the contact holes 34 and 35 and flattened asshown in FIG. 3(d), so that a current perpendicular to the plane typethin-film magnetic head having a top electrode 36 having a shape whichis curved and converges toward the CPP type magnetoresistance effectfilm 14 is obtained on the CPP type magnetoresistance effect film 14. Inthis embodiment, Cu was used as the material of the top electrode 36. Asthe material of this electrode, other materials than Cu may be used.

According to this producing method in the second embodiment, the topelectrode 36 formed on the CPP type magnetoresistance effect film 14 hasa shape which is curved and converges toward the CPP typemagnetoresistance effect film 14, so that the distance between the topand bottom electrodes 10 a and 36 increases as approaching themagnetization fixing film 18. Thus, even if a large current is caused toflow between the bottom electrode 10 a and the top electrode 36, it ispossible to prevent the direction of magnetization of the magnetizationfixing film from being disturbed by the magnetic field due to thecurrent, and it is possible to decrease the dispersion in direction ofmagnetization of the CPP type magnetoresistance effect film 14. Inaddition, it is possible to decrease the leakage current from the cornerportions of the electrodes 10 a and 36 to cause a large sense current toflow between the electrodes 10 a and 36, and it is possible to obtain alarge reproducing output.

In this second embodiment, the positioning precision between the CPPtype magnetoresistance effect film 14 and the top electrode 36 can beimproved as compared with that in the first embodiment.

Furthermore, in the producing method in the second embodiment, thecurved recessed portion 34 is formed in the insulating film 30 by theisotropic etching, and thereafter, the converging opening portion 35communicated with the CPP type magnetoresistance effect film 14 isformed by the anisotropic etching. However, curved or converging openingportions 34 and 35 communicated with the CPP type magnetoresistanceeffect film 14 may be formed in the insulating film 30 only by theisotropic etching by adjusting the thickness of the insulating film 30and etching conditions.

When a current was caused to flow between electrodes with respect to acurrent perpendicular to the plane type thin-film magnetic head using amagnetoresistance effect element wherein the top electrode thus obtainedon the CPP type magnetoresistance effect film 14 had a shape whichconverges toward the CPP type magnetoresistance effect film 14 and whichwas produced in the first and second embodiment, and a conventionalcurrent perpendicular to the plane type thin-film magnetic head shown inFIG. 6, reproducing outputs (output voltages) corresponding to themagnetoresistance effect were measured. The results thereof are shown inFIG. 4. As shown in FIG. 4, the output voltage of the conventionalthin-film magnetic head is saturated when the current is about 50 mA,whereas the output voltage of the thin-film magnetic head using themagnetoresistance effect element in this embodiment does not tend to besaturated until the current reaches about 100 mA. Thus, it can beclearly seen that the structure of the thin-film magnetic head using themagnetoresistance effect element produced according to the presentinvention is also very effective from the standpoint of the reduction ofthe magnetic field due to leakage current.

(Third Embodiment)

FIG. 8 shows the construction of the third embodiment of amagnetoresistance effect element according to the present invention. Themagnetoresistance effect element in this third embodiment comprises: amagnetic shield film 54 which is formed on a substrate 52; a bottomelectrode film 56 which is formed on the magnetic shield film 54 andwhich has a top face having a substantially flat protruding portion; aninsulating film 58 which is formed on a recessed portion of the bottomelectrode 56 and which has the same surface as the top face of thebottom electrode 56; a CPP type magnetoresistance effect film 60 whichis formed so as to cover the top face of the bottom electrode 56; amagnetization fixing layer (not shown) which is provided outside of themagnetoresistance effect film 60; an insulating film 62 which is formedso as to cover the magnetoresistance effect film 60 and which has afirst tapered opening portion on the protruding portion of the bottomelectrode 56; an insulating film 64 which is formed on the insulatingfilm 62, the insulating film having a second opening portion which isarranged at a position corresponding to the first opening portion andwhich converges upwards as leaving the center of the first openingportion in a direction parallel to the film plane of themagnetoresistance effect film 60; a top electrode 66 which is formed soas to be filled in the opening portions of the insulating films 64 and62; a magnetic shield film 68 which is formed on the top electrode 66;and a protective film 70 which is formed on the magnetic shield film 68.

That is, in the magnetoresistance effect element in this embodiment, theshapes of the bottom electrode 56 and top electrode 66 on their crosssections perpendicular to the film plane of the magnetoresistance effectfilm 60 converge toward the magnetoresistance effect film 60.

If the shapes of the bottom electrode 56 and top electrode 66 on theircross sections perpendicular to the film plane of the magnetoresistanceeffect film 60 are formed so as to converge toward the magnetoresistanceeffect film 60 as the magnetoresistance effect element in thisembodiment, it is possible to decrease the leakage current from the edgeportions of the bottom electrode 56 and top electrode 66. As a result,it is possible to cause a large sense current to flow through themagnetoresistance effect film 60 to increase the variation in resistanceof the magnetoresistance effect film 60, so that it is possible toobtain a high reproducing output and improve the withstand voltage. Inaddition, even if a large current is caused to flow between the topelectrode 66 and the bottom electrode 56, it is possible to prevent thedirection of magnetization of the magnetization fixing film from beingdisturbed by the magnetic field due to the current.

Referring to FIGS. 9 through 11, a method for producing the thirdembodiment of a magnetoresistance effect element according to thepresent invention will be described below.

First, after a magnetic shield 54 of, e.g., Ni₈₀Fe₂₀, having a thicknessof 300 nm is formed on a substrate 52, a bottom electrode 56 of a copperthin film having a thickness of 100 nm is formed by a usual sputteringmethod (see FIG. 9(a)).

Then, after an electron beam exposing resist having a thickness of 100nm was applied to the bottom electrode 56, a predetermined remainingpattern 57 (a diameter of 100 nm in this embodiment) was formed withelectron beams by exposure and development (see FIG. 9(a)).Subsequently, after the substrate was irradiated with Ar ions at anincident angle of about 20 degrees to carry out etching, the resist 57was removed to form a bottom electrode 56 having a protruding portionhaving a height of about 50 nm (see FIG. 9(b)).

Then, after an aluminum oxide (Al₂O₃) film 58 having a thickness ofabout 100 nm was formed on the whole surface by the sputtering method(see FIG. 9(c)), it was etched back to be flattened by the CMP or thelike (see FIG. 9(d)). As a result, the irregularities on the protrudingportion of the bottom electrode 56 and on the surface of the aluminumoxide film 58 were 10 nm or less, so that surface performance was good.

After a signal extracting pad (not shown) and so forth are formed on thesubstrate thus flattened, a magnetoresistance effect film 60 isdeposited (see FIG. 10(a)). The magnetoresistance effect film has aconstruction of 5 nm Ta/10 nm PtMn/3 nm CoFe/3 nm Cu/2 nm CoFe/5 nm Tafrom the bottom electrode 56.

Thereafter, an I-line exposure system and a two-layer resist (T shape)are used for forming a resist pattern 61 having a size of about 500nm×500 nm on the magnetoresistance effect film 60 (see FIG. 10(b)).Subsequently, this resist pattern is used as a mask for etching themagnetoresistance effect film 60 with Ar ions to form themagnetoresistance effect film 60 (see FIG. 10(c)). Then, after a CoPtfilm having a thickness of 20 nm is deposited as a magnetization fixinglayer (not shown), the resist pattern 61 is removed to form amagnetization fixing layer.

Then, after a silicon oxide (SiO₂) film 62 having a thickness of 30 nmis deposited by the reactive sputtering method, an electron beamexposing resist having a thickness of 100 nm is applied, and apredetermined extracting pattern 73 (φ100 nm in this embodiment) isformed with electron beams by exposure and development (see FIG. 10(d)).By patterning the silicon oxide film 62 by the RIE method, a contacthole 62 a for forming a top electrode 66 is obtained (see FIG. 11(a)).Then, after a self-condensing organic matter 63 was applied on thesubstrate having the contact hole 62 a, baking (30 minutes at 200° C.)was carried out to cause the self-condensing organic matter 63 to bedroplets on the contact hole 62 a (see FIG. 11(b)). In this case, sincethe wettability of the silicon oxide film 62 is different from that ofTa of the outermost surface layer of the magnetoresistance effect film60, it is not particularly required to carry out any hydrophilictreatments.

Then, after a silicon oxide (SiO₂) film 64 having a thickness of 20 nmis deposited by the reactive sputtering method on the contact hole onwhich the organic matter has been self-condensed, the self-condensedorganic matter 63 is removed (see FIG. 11(c)). Thereafter, a copper filmwas deposited by a usual sputtering method so as to have a thickness of100 nm, and an electrode patterning was carried out to form a topelectrode 66 (see FIG. 11(d)).

Then, as shown in FIG. 8, after a magnetic shield 68 of, e.g., Ni₈₀Fe₂₀,having a thickness of 300 nm was formed as a top magnetic shield layer,signal extracting portions of the bottom electrode 56 and top electrode66 were formed, and thereafter, an aluminum oxide film 70 having athickness of 20 μm was deposited as a protective film.

Finally, after bar working and chip working were carried out to examinethe outputs of heads, it was found that a head in this embodiment havingthe bottom and top electrodes 56 and 66 converging toward themagnetoresistance effect film 60 has a higher withstand voltage by about30% than that of a head which does not converge, and can obtain a highoutput voltage with a low current.

As described above, according to a method for producing amagnetoresistance effect element according to the present invention, itis possible to cause a large sense current to flow between electrodes,and it is possible to decrease the dispersion in direction ofmagnetization of a CPP element based on a magnetic current due to thecurrent and increase a reproducing output.

While the present invention has been disclosed in terms of theembodiment in order to facilitate better understanding thereof, itshould be appreciated that the invention can be embodied in various wayswithout departing from the principle of the invention. Therefore, theinvention should be understood to include all possible embodiments andmodification to the shown embodiments which can be embodied withoutdeparting from the principle of the invention as set forth in theappended claims.

What is claimed is:
 1. A method for producing a magnetoresistance effectelement comprising: after forming a first electrode, forming amagnetoresistance effect film on the first electrode; forming aninsulating film on the magnetoresistance effect film; isotropic-etchingthe insulating film to form a curved recessed portion in the insulatingfilm by using a mask having an opening portion, the position of whichmatches with the position of the magnetoresistance effect film; etchingthe insulating film to expose the top surface of the magnetoresistanceeffect film; and forming a second electrode in the recessed portion. 2.A method for producing a magnetoresistance effect element as set forthin claim 1, wherein: the step of etching the insulating film to exposethe top surface comprises forming a converging opening portion, which iscommunicated with the magnetoresistance effect film, in the insulatingfilm by an anisotropic etching, and the step of forming the secondelectrode film comprises filling the converging opening portion and thecurved recessed portion with an electrode material film.
 3. A method forproducing a magnetoresistance effect element as set forth in claim 1,further comprising after forming the magnetoresistance effect film,forming a magnetization forming film that overlaps with a part of thetop surface of the magnetoresistance effect film.
 4. A method forproducing a magnetoresistance effect element as set forth in claim 1,wherein the insulating film is formed by reactive sputtering.
 5. Amethod for producing a magnetoresistance effect element as set forth inclaim 1, wherein the isotropic etching comprises chemical dry etching.6. A method for producing a magnetoresistance effect element as setforth in claim 2, wherein the anisotropic etching comprises reactive ionetching.
 7. A method for producing a magnetoresistance effect element asset forth in claim 2, wherein the second electrode has a shape that iscurved and converges toward the magnetoresistance effect film.
 8. Amethod for producing a magnetoresistance effect element as set forth inclaim 2, wherein the magnetoresistance effect film comprises a filmconfigured to be substantially perpendicular a current applied to theelement.
 9. A method for producing a magentoresistance effect element asset forth in claim 1, wherein the mask comprises a resist pattern.
 10. Amethod for producing a magnetoresistance effect element as set forth inclaim 1, wherein: the step of etching the insulating film to expose thetop surface comprises forming a converging opening portion, which iscommunicated with the magnetoresistance effect film, in the insulatingfilm by an isotropic etching, and the step of forming the secondelectrode film comprises filling the converging opening portion and thecurved recessed portion with an electrode material film.